From a new working paper by Bryan Lutz and Louise Sheiner.

A major factor weighing down the long-term finances of state and local governments is the obligation to fund retiree benefits. While state and local government pension obligations have been analyzed in great detail, much less attention has been paid to the costs of the other major retiree benefit provided by these governments: retiree health insurance. The first portion of the paper uses the information contained in the annual actuarial reports for public retiree health plans to reverse engineer the cash flows underlying the liabilities given in the report. Obtaining the cash flows allows us to construct liability estimates which are consistent across governments in terms of the discount rate, actuarial method and assumptions concerning medical cost inflation and mortality…Relative to pension obligations discounted at the same rate, we find that unfunded retiree health care liabilities are 1/2 the size of unfunded pension obligations.

Perhaps the most interesting aspect of the paper is the amount of effort it took on their part to find the data to do the calculations. Similarly, one of the biggest challenges for Reinhart and Rogoff is to find data on government debt outstanding. There are strong incentives for politicians to avoid transparent accounting, and not much in the way of countervailing power.